1. Field of the Invention
The present invention relates to a process for the preparation of a novel antistatic agent capable of imparting a permanent antistatic effect to a methacrylic resin, and to a methacrylic resin composition to which a permanent antistatic effect is given by an antistatic agent prepared according to this process.
2. Description of the Related Art
A methacrylic resin is used for illuminators, signboards, construction materials, decorative articles and the like because it has an excellent transparency, a good surface gloss, a pleasing appearance, and good mechanical properties. Nevertheless, since the methacrylic resin has a high surface resistance, dust or dirt is adsorbed to mar the appearance and an electric shock is given to the human body, an electronic part and the like.
As the means for imparting an antistatic effect to a methacrylic resin, there have been adopted such methods as (1) blending a surface active agent, and (2) surface coating with a surface active agent.
Furthermore, a method is proposed in which a methyl methacrylate type monomer is random-copolymerized with a methacrylate or acrylate monomer having a quaternary ammonium salt (see Japanese Examined Patent Publication No. 48-15471 and Japanese Examined Patent Publication No. 54-23395).
Of the methods using a surface active agent, the method using a compound containing a cationic quaternary ammonium salt is especially effective. But, if it is intended to obtain a desired antistatic property by blending this surface active agent, a large quantity of the surface active agent must be added, and thus the excellent characteristics of the methacrylic resin, such as the excellent transparency and good mechanical properties are sacrificed. The method of the surface coating with such a surface active agent is simple, but involves a problem with regard to the durability of the effect, and the effect is readily lost by water washing or abrasion. The proposal of copolymerizing a methyl methacrylate type monomer with a methacrylate type or acrylate type monomer having a quaternary ammonium salt group as the comonomer involves a problem with regard to the heat resistance or the release property from a mold because another monomer or low-molecular-weight material is used as a common solvent for the quaternary ammonium salt monomer and the methyl methacrylate type monomer. The random polymerization has a problem such that, since the quaternary ammonium salt group is randomly distributed in the entire polymer, it is difficult effectively to utilize all of the quaternary ammonium salt, and a large quantity of the quaternary ammonium salt must be used for the manifestation of the intended effect, and thus the transparency and heat resistance are adversely influenced with the result that it is difficult to maintain a good balance among the characteristics.